Add a ProxyScriptFetcher class for doing asynch downloads of PAC scripts....

net/proxy/proxy_script_fetcher.h

+// Copyright (c) 2008 The Chromium Authors. All rights reserved.  Use of this
+// source code is governed by a BSD-style license that can be found in the
+// LICENSE file.
+
+// ProxyScriptFetcher is an async interface for fetching a proxy auto config
+// script. It is specific to fetching a PAC script; enforces timeout, max-size,
+// status code.
+
+#ifndef NET_PROXY_PROXY_SCRIPT_FETCHER_H_
+#define NET_PROXY_PROXY_SCRIPT_FETCHER_H_
+
+#include "net/base/completion_callback.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"
+
+class GURL;
+class URLRequestContext;
+
+namespace net {
+
+class ProxyScriptFetcher {
+ public:
+  // Destruction should cancel any outstanding requests.
+  virtual ~ProxyScriptFetcher() {}
+
+  // Downloads the given PAC URL, and invokes |callback| on completion.
+  // On success |callback| is executed with a result code of OK, and a
+  // string of the response bytes. On failure, the result bytes is an empty
+  // string, and the result code is a network error. Some special network
+  // errors that may occur are:
+  //
+  //    ERR_TIMED_OUT         -- the fetch took too long to complete.
+  //    ERR_FILE_TOO_BIG      -- the response's body was too large.
+  //    ERR_PAC_STATUS_NOT_OK -- non-200 HTTP status code.
+  //    ERR_NOT_IMPLEMENTED   -- the response required authentication.
+  //
+  // If the request is cancelled (either using the "Cancel()" method or by
+  // deleting |this|), then no callback is invoked.
+  //
+  // Only one fetch is allowed to be outstanding at a time.
+  virtual void Fetch(const GURL& url, std::string* bytes,
+                     CompletionCallback* callback) = 0;
+
+  // Aborts the in-progress fetch (if any).
+  virtual void Cancel() = 0;
+
+  // Create a ProxyScriptFetcher that uses |url_request_context|.
+  static ProxyScriptFetcher* Create(URLRequestContext* url_request_context);
+
+  // --------------------------------------------------------------------------
+  // Testing helpers (only available to unit-tests).
+  // --------------------------------------------------------------------------
+ private:
+  FRIEND_TEST(ProxyScriptFetcherTest, Hang);
+  FRIEND_TEST(ProxyScriptFetcherTest, TooLarge);
+
+  // Sets the maximum duration for a fetch to |timeout_ms|. Returns the previous
+  // bound.
+  static int SetTimeoutConstraintForUnittest(int timeout_ms);
+
+  // Sets the maximum response size for a fetch to |size_bytes|. Returns the
+  // previous bound.
+  static size_t SetSizeConstraintForUnittest(size_t size_bytes);
+};
+
+}  // namespace net
+
+#endif  // NET_PROXY_PROXY_SCRIPT_FETCHER_H_